Our work proposed for the coming year will concentrate in four areas: (A) To identify additional constituents in fluid which surrounds the spermatozoa in the epididymis and to study the effects of such constituents on the metabolism, motility and fertilizing ability of testicular spermatozoa stored in vitro. (B) To investigate the penetration of various isotopically labeled compounds from the systemic blood into the lumen of the ductus epididymis and to determine their subsequent incorporation into, and utilization by, epididymal spermatozoa. (C) To study the effects of i.v. or i.m. injected LH, FSH, testosterone, prolactin and specific prolactin inhibitor (ergot alkaloids) on the metabolism of glucose by freshly collected testicular spermatozoa and to relate this activity to androgen levels in rete fluid. (D) To determine the role of androgen-binding protein in rete testis fluid in bringing androgens in close proximity with the spermatozoa and to study the effects of this protein on sperm maturation. BIBLIOGRAPHIC REFERENCES: Bartke, A. and J.K. Voglmayr. Effects of gonadotropins on androgen levels in rete testis fluid of the ram. Biol. Reprod. 16: 274-280,1977. Voglmayr, J.K., N.A. Musto, S.K. Saksena, P.D.C. Brown-Woodman, P.B. Marley and I.G. White. Characteristics of semen collected from the cauda epididymis of conscious rams. J. Reprod. Fert. 49: 245-251, 1977.